As is known in the art, there exists a class of circuits referred to as “flat plate assemblies.” In general, flat plate assemblies are comprised of two or more plate-like structures bonded together. So-called “flat-plate antennas” and other radio frequency (RF) flat plate assemblies are provided from electronically conductive plates having flat surfaces with printed circuit boards (PCBs) disposed therebetween. The plates in such assemblies are often bonded using an adhesive such as a conductive epoxy. One important factor to consider when bonding plates is a thickness of a line of adhesive disposed between the plates (also referred to as a bond line). If an inadequate bond line is used, the plates are not securely bonded together. Thus, the risks of an inadequate bond line include, but are not limited to, low connection strength, poor electrical properties and high thermal resistance between the plates.
Bond line thickness is difficult to control during process and manufacturing cycles. Attempts to control the volume and location of conductive epoxies or other adhesives used for bonding plates together have been process-focused. For example, automated dispense equipment and volumetric statistical process control (SPC) measurements have been used to help control an amount and location of a dispensed epoxy or adhesive. Even with such controls, however, during a cure part of a bonding process, capillary action may cause an adhesive to wick out of a bond channel between flat surfaces of the plates being bonded. This can result in voids in the bond and/or the existence of adhesive in an RF signal path (e.g. due to having an excess amount of adhesive forced into the RF signal path when plates are secured together). A void in an epoxy bondline and/or the existence of a conductive adhesive in an RF signal path can result in degradation of electrical and/or mechanical performance characteristics of the flat plate assembly.
This problem has been controlled to some degree by fabricating or otherwise providing so-called “adhesive lines” on flat areas of plates to be bonded. Such adhesive lines act as dams intended to prevent wicking of the bond material. This approach, however, is time consuming and often requires multiple iterations to arrive at a reasonable configuration of adhesive lines. Additionally, when bonding plates, cure operations are “blind” so the results can only be inspected after bonding the plates. Thus, insufficient bonds are often only discovered after undertaking the time and expense of manufacturing the flat plate assembly.